Prior switching networks of the type which employ a selected plurality of row address bits to determine the routing of connection paths between adjacent columns of interconnecting switches have been implemented in accordance with precise algorithms such that each network node size requires a unique wiring topology and various different kinds of switching cards. The networks of this invention provide for communication paths between a structure of identical switches in a network of this type in accordance with a routing algorithm, which assigns address routing bits so that predefined network cards may be used to expand the network from a small number of network nodes to a larger number of nodes.
Prior networks of this kind were constructed with switches having point-to-point connections between them. The network established connections from requestor devices to responder devices by relaying "requests" and "responses" through the switches. Each switch had built-in control logic to route both requests and responses. The switch setting was determined by using the comparison of the request with the request's current location in the network. Each switch routed the requests using only the information contained in the requests and the local switch to provide distributed routing without a centralized controller. The switch setting was remembered to route the responses on the same paths as the associated request but in the reverse direction.
These networks were constructed so that a switch could route a signal to another switch that has the same switch number except for a single binary digit in the next stage. A request contains a binary number identifying the desired response port. The switch compared the request with the switch number. If the binary digit compared was the same, the request was routed on a binary straight path; otherwise the request was routed to another switch that matched the digit in the request. At the end of the network, the request should have reached the switching output stage whose switch number exactly matched the request. The present invention employs similar switching techniques, but response messages are not necessarily required.